The human body is only capable of effective performance and survival within a relatively narrow range of temperatures. Hence, the body includes temperature control systems to maintain optimal bodily function and health. In particular, the human body is configured to sweat moisture through the skin so that when this moisture evaporates, evaporative cooling takes place on the surface of the skin to cool the individual. When excessive cold is encountered, the body may initiate a shivering reflex such that additional heat is generated to compensate. These and other body temperature systems are not entirely adequate to deal with all of the ranges of temperature which a human is likely to encounter in many circumstances. Hence, it has been known throughout the ages for individuals to augment their own body temperature control systems with appropriate clothing. When colder temperatures are encountered, warmer clothing is worn. When hotter temperatures are encountered less and lighter clothing is worn; or alternatively clothing which tends to reflect sunlight or which enhances the prevalence of shade.
While the wearing of different amounts of clothing is generally effective in compensating for excessively cold environments, climates exist where temperatures are sufficiently high that clothing modifications alone are not sufficient to maintain optimal body temperature and personal performance. In particular, deserts present a challenging environment in that temperatures up to or even exceeding 140 degrees Fahrenheit can be encountered. When other features of the desert environment (including lack of trees or other shade structures, and radiation of heat from the ground and surrounding structures) is taken into account, the heat load on an individual can further tax the natural and artificial systems used by the individual to maintain adequate body temperature for optimal personal performance in the desert environment.
In such environments the evaporative cooling associated with sweating and maintaining body temperature requires that exceptionally large amounts of fluids be consumed. With the consumption of such large amounts of liquid, electrolyte balances within the individual are difficult to maintain and other difficulties are also encountered, including the uncomfortableness associated with excessive sweating. Accordingly, a need exists for improved systems for actively cooling the body of an individual when the individual is in a high temperature environment, such as a desert.
Likewise, hot jungle temperatures, although lower than in the desert, with humidity approaching 100% and eliminating effective use of evaporative cooling of the body by sweat or by artificial evaporation of water, present a need for improved body cooling systems.